The present invention relates to a microwave oven, and more particularly, to a structure of hooded microwave oven in which exhaust and cooling airflow passages are independently formed and an exhaust filter is mounted only in the exhaust airflow passage so as to increase operating efficiency and to reduce flow noise.
First, the constitution of a conventional hooded microwave oven will be described in detail with reference to FIG. 1. FIG. 1 is a perspective view of the conventional hooded microwave oven with an outer case thereof removed and an air duct thereof disassembled.
As shown in FIG. 1, a cavity 2 in which cooking is done is formed at one side of the microwave oven. An electric equipment installation chamber 4 is formed at one side of the cavity 2. A plurality of electric equipments 4xe2x80x2 are mounted inside the chamber 4. In addition, a blowing fan 8 is mounted on the top of the chamber 4 to form a cooling air stream fd toward the chamber 4.
Furthermore, an exhaust inflow opening 6 is formed in the rear of a back wall of the chamber 4. The exhaust inflow opening 6 serves as a passage allowing hot air and smoke discharged from a gas oven range (not shown) installed under the microwave oven to flow into the microwave oven.
On the other hand, an air inflow portion 2a and an air outflow portion 2b, which are constructed by a plurality of passage holes and allow the air to flow into and out of the cavity 2, respectively, are formed on a top surface of the cavity 2. Additionally, a guide wall 2xe2x80x2, which is placed adjacent the air inflow portion 2a to guide the air toward the air inflow portion 2a, is formed on the top surface of the cavity 2.
Moreover, an air duct 22 is mounted on the top of the cavity 2. The air duct 22 is a structure for guiding a sucked exhaust air stream fe of heat and smoke generated from the gas oven range (not shown) installed under the microwave oven toward the front side of the cavity 2. Engaging protrusions 22c are formed at a leading end of the air duct 22. Also, at the opposing positions of right and left side walls 22a, 22b of the air duct 22, a pair of support protrusions 22axe2x80x2, 22bxe2x80x2 projecting from the respective side walls 22a, 22b are provided. Incline surfaces sloping up toward the rear of the air duct 22 are formed on top ends of the support protrusions 22axe2x80x2, 22bxe2x80x2, respectively.
Additionally, an air introduction portion 22d is formed outside the left side wall 22b of the air duct 22. The air introduction portion 22d has a passage hole in the center portion thereof, and is formed in the shape surrounded by four side walls so as to guide the air downwardly through the passage hole. Furthermore, the air fc1 that is flowed into the air introduction portion 22d is guided by the guide wall 2xe2x80x2 toward the air inflow portion 2a (fc2).
Moreover, a ventilation motor 32c provided with output shafts (not shown) at both ends thereof is mounted in the rear of the air duct 22. Sirocco fans 32c are mounted at the right and left sides of the ventilation motor 32c, respectively. The sirocco fans suck air in the direction of the output shafts (not shown) and discharge the air in the direction orthogonal to the output shafts (not shown). Hereinafter, the left sirocco fan is referred to as a left fan 32b, and the right sirocco fan is referred to as a right fan 32a. 
In addition, exhaust openings 32axe2x80x2, 32bxe2x80x2 are formed respectively at one side of each sirocco fan. The exhaust openings 32axe2x80x2, 32bxe2x80x2 is directed to the air duct 22 to be described below.
Also, an exhaust filter 22xe2x80x2 is mounted at a front side of the air duct 22. That is, a lower edge of the exhaust filter 22xe2x80x2 is supported by the engaging protrusions 22c at the leading end of the air duct 22 and a rear surface of the exhaust filter 22xe2x80x2 is supported by the incline surfaces at the top ends of the support protrusions 22axe2x80x2, 22b40  so that the exhaust filter 22xe2x80x2 is mounted at the front side of the air duct 22 to thoroughly cover the front side of the air flow passage formed in the air duct 22. Absorbent material is densely filled in the exhaust filter 22xe2x80x2. By means of the absorbent material, toxic substance in the exhaust discharged through the air duct 22 is filtered so that clean air is discharged from the front side of the exhaust filter 22xe2x80x2.
On the other hand, FIG. 2 shows a state that the air duct 22 is mounted on the top of the cavity. Thus, since the air inflow portion 2a and the air outflow portion 2b, which are formed on the top surface of the cavity 2, are placed under the air duct 22, they are hidden. Moreover, at the leading end of the air duct 22, the exhaust filter 22xe2x80x2 is obliquely mounted to slope toward the rear of the air duct 22.
Hereinafter, the flow of air formed inside the microwave oven in the prior art constructed as such will be described with reference to FIG. 2.
When the ventilation motor 32c is operated, contaminated air produced from the gas oven range (not shown) installed under the microwave oven is sucked through the right and left fans 32a, 32b of the ventilation motor 32c into the microwave oven and flows as indicated by the arrow fe. That is, one portion of the contaminated air flowed into the rear side of the electric equipment installation chamber 4 of the microwave oven through exhaust inflow opening 6 flows toward the right fan 32a, and the other portion of the contaminated air flows toward the left fan 32b. 
Meanwhile, as for the flow of air inside the cavity 2, air drawn into the microwave oven through a ventilation grill (not shown) installed at the left top side of the front of the cavity 2 flows toward the air inflow portion 2a through the air introduction portion 22d as indicated by the arrow fc1. In addition, air drawn into the cavity 2 through the air inflow portion 2a evaporates moisture within the cavity 2, and the air containing the evaporated vapor is discharged from the top of the cavity 2 through the air outflow portion 2b. The air discharged from the air outflow portion 2b flows into the right fan 32a of the ventilation motor 32c. 
As a result, the contaminated air discharged from the gas oven range (not shown) flows through the left fan 32b of the ventilation motor 32c, whereas not only the contaminated air but also the air containing the vapor in the cavity flows through the right fan 32a. 
As described above, the air sucked into the ventilation motor 32c is discharged through each exhaust openings 32axe2x80x2, 32bxe2x80x2 to the air duct 22, and passes through the exhaust filter 22xe2x80x2 mounted at the leading end of the air duct 22 so as to be discharged forward of the microwave oven. Electric equipments 4xe2x80x2 in the electric equipment installation chamber 4 are cooled by a separate blowing fan 8 which forms a stream of air by sucking the outside air.
However, the microwave oven having such structure in the prior art gives rise to problems as follows.
First, the contaminated air to be flowed into the right and left fans 32a, 32b of the ventilation motor 32c is generated only when the gas oven range is in operation. That is, when only the microwave oven is operated, the contaminated air does not flow into the right and left fans 32a, 32b of the ventilation motor 32c. However, even in such case, uncontaminated air discharged forward of the air duct 22 through the right fan 32a also unnecessarily passes through the exhaust filter 22xe2x80x2.
Accordingly, in such case, there is a problem in that the exhaust filter 22xe2x80x2 does not function as a filter, but obstructs the flow of air passing through the right fan 32a. In addition, noise is made when the air passes through a dense filler within the exhaust filter 22xe2x80x2.
Moreover, due to the exhaust filter 22xe2x80x2, discharging velocity of the air discharged from the right fan 32a is lowered so that air does not circulate smoothly in the cavity 2. Thus, the vapor in the cavity 2 is not discharged smoothly.
Furthermore, since the exhaust filter 22xe2x80x2 does not have a structure for regulating its upward movement, it is often disengaged from the air duct 22 when an external force is applied thereto or it is moved. Then, there is also a problem in that the contaminated air is discharged without being filtered by the exhaust filter 22xe2x80x2.
Therefore, it is an object of the present invention to solve the problems of the prior art as mentioned above, more particularly, to make the flow of air within hooded microwave oven smoother.
It is another object of the present invention to minimize noise caused by the flow of air within the hooded microwave oven.
It is a further object of the present invention to make the flow of air within a cavity of the hooded microwave oven smooth.
It is a still further object of the present invention to form the flow of air within the microwave oven with relatively small number of components.
It is a still further object of the present invention to ensure the filtration of air by installing an exhaust filter more firmly.
According to features of the present invention for achieving the above objects, a hooded microwave oven comprises a cavity in which cooking is done; an electric equipment installation chamber which is formed at one side of the top of the cavity and in which electric equipments are mounted; a ventilation motor assembly which forms a flow of air for cooling the electric equipments and a flow of contaminated air by a hood function; and an air duct which independently separates the flow of contaminated air and the flow of air for cooling that are sucked into and discharged from the ventilation motor assembly and which has an exhaust filter mounted at a portion through which the contaminated air passes.
The ventilation motor assembly may be provided with fans at both ends of a ventilation motor, respectively, and the air duct is provided with a first and second duct portions which separately communicate with the respective fans.
The exhaust filter may be detachably and obliquely installed, from the front of the air duct, on the duct portion through which the contaminated air passes.
The air duct may be provided with support protrusions of which top ends slope to support obliquely a rear surface of the exhaust filter, thereby mounting the exhaust filter; top end protrusions which press and support one side of a top surface of the exhaust filter are provided at both sides of a leading end of the air duct; and engaging protrusions which engage a leading end of the exhaust filter are formed at the leading end of the air duct.
The electric equipment installation chamber in which the electric equipments are installed may be formed at a level adjacent to the fan of the ventilation motor.
The fan of the ventilation motor may suck air from the electric equipment installation chamber and may form a flow of air in the chamber.
According to the present invention having such constitution, efficient flow of air can be obtained since the flow of air for the hood function and the flow of air for cooling are separated, and the effect that a storing space of the cavity can be expanded horizontally by forming the electric equipment installation chamber at the top of the cavity can be expected, and the ventilation motor can be utilized efficiently because both the flow of air for cooling the electric equipments and the flow of air for the hood function can be carried out by one ventilation motor.